This invention relates to a medical device delivery catheter system, such as the kind used in percutaneous transluminal coronary angioplasty (PTCA) procedures. More particularly, it relates to a medical device delivery catheter employing a movable balloon which is disposed about the medical device.
In typical PTCA procedures, a guiding catheter is percutaneously introduced into the cardiovascular system of a patient and advanced through the aorta until the distal end is in the ostium of the desired coronary artery. Using fluoroscopy, a guide wire is then advanced through the guiding catheter and across the site to be treated in the coronary artery. An over the wire (OTW) balloon catheter is advanced over the guide wire to the treatment site. The balloon is then expanded to reopen the artery. The OTW catheter may have a guide wire lumen which is as long as the catheter or it may be a rapid exchange catheter wherein the guide wire lumen is substantially shorter than the catheter. Alternatively, a fixed wire balloon catheter could be used. This device features a guide wire which is affixed to the catheter and cannot be removed. Following dilatation of the vessel, the balloon catheter is removed from the vessel.
To help prevent arterial closure, repair dissection, or prevent restenosis following dilatation, a physician can implant an intravascular prosthesis, or a stent or other such device such as a stent-graft, or a graft, for maintaining vascular patency inside the artery at the lesion. The stent may either be a self-expanding stent or a balloon expandable stent. For the latter type, the stent is often delivered on a balloon and the balloon is used to expand the stent. The self-expanding stents may be made of shape memory materials such as nitinol or constructed of regular metals but of a design which exhibits self expansion characteristics.
In certain known stent delivery catheters, a stent and an optional balloon are positioned at the distal end of the catheter, around a core lumen. The stent and balloon are held down and covered by a sheath or sleeve. When the distal portion is in its desired location of the targeted vessel the sheath or sleeve is retracted to expose the stent. After the sheath is removed, the stent is free to self-expand or be expanded with a balloon.
This multiple step procedure of dilatation with a balloon catheter, removal of the balloon catheter and use of a separate stent delivery catheter is time consuming and requires the use of many different devices. Moreover, the insertion and removal of multiple device increase the opportunity for hemorrhagic complications and increase the overall trauma to the patient. In an effort to reduce the number of insertions and removals of catheters, a number of devices have been disclosed which combine a dilation balloon and a stent delivery catheter in a single device. These devices reflect a variety of approaches.
One approach employs a multiple balloon catheter in which a first balloon is used for dilatation and a second balloon is used for expanding a stent. This approach is disclosed, inter alia, in U.S. Pat. Nos. 5,733,299, 5,632,760, 5,456,694 and 5,725,535.
Another approach employs a balloon which is longitudinally displaceable with respect to the stent. This approach is disclosed, inter alia, in U.S. Pat. No. 5,807,398 and 5,634,928.
The present invention presents another approach to providing a dilatation balloon in a medical device delivery catheter.
For the purpose of this disclosure, the term medical device shall refer to stents, stent-grafts, grafts and vena cava filters.
All U.S. patents and patent applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
The present invention provides an improved medical device delivery system. The medical device delivery system comprises a catheter having an inner tube with a medical device disposed about a receiving region at the distal end thereof and a retractable balloon assembly surrounding at least the medical device. The retractable balloon assembly may comprise a medical balloon in mechanical communication with a balloon retraction device and an inflation lumen in fluid communication with the medical balloon. In one embodiment, the balloon retraction device comprises an outer sheath and an inner sheath. The proximal end of the balloon is attached to the distal end of the outer sheath, and the distal end of the balloon is attached to the distal end of the inner sheath.
The outer sheath of the catheter may include a proximal outer sheath portion and a retractable distal sheath. An optional collapsible sheath may be located between and adhered to the proximal outer sheath and the retractable distal sheath. During retraction of the distal sheath the collapsible sheath collapses upon itself or accordions upon its preformed pleats or creases, providing room for the distal sheath to retract unencumbered, thereby freeing the loaded stent. The inclusion of the collapsible sheath significantly reduces the sheath length, maintains a reduced system profile, provides good flexibility and provides a protective covering to the w ire pull back mechanism.
The outer sheath may also be telescoping. A separate inflation lumen may be provided or the space between an inner and outer sheath may serve as an inflation lumen.